The present invention relates generally to motorized vehicles and, more particularly, to an adjustable suspension system for such vehicles.
Over the past decade, vehicles capable of off-road driving, e.g., sport utility vehicles (SUVs), have become increasingly popular. For off-road driving, these vehicles require increased ride height, i.e., ground clearance, to avoid obstacles, e.g., rocks, bumps, and other irregularities, and to provide the distance required to absorb the additional forces caused by such obstacles. This increased ride height also brings a number of disadvantages, however, including high roll center, high effective frontal area, decreased stability, decreased cornering ability, and lower fuel economy. As such, the increased ride height required for off-road driving is not well suited for high-speed travel on smooth, paved surfaces.
An ideal suspension system would provide a low ride height for medium and high speed travel on smooth, paved surfaces and a high ride height for low to medium speed travel on unpaved, irregular surfaces. With such an ideal suspension system, high-speed operation would occur only at low ride height, thereby optimizing cornering ability, fuel economy, traction, and safety. Unfortunately, conventional single-pivot suspension systems do not allow for any significant adjustment in ride height without sacrificing suspension performance and causing uneven tire wear. Typically, a coil spring or spring/damper can be used to adjust the ride height of a single-pivot suspension system. However, the amount of adjustment that can be made before significant adverse effects on wheel camber, ride harshness, and safety occur is minimal. To be commercially viable, a suspension system should have a useful adjustment range of at least 6 inches to 8 inches without adversely impacting the ride quality, cornering performance, or tire life. This range of adjustment is not possible with conventional single-pivot suspension systems.
In view of the foregoing, there is a need for an adjustable suspension system that enables the ride height of a vehicle to be adjusted over a wide range without sacrificing handling, performance, tire wear, or safety.
Broadly speaking, the present invention fills this need by providing an adjustable suspension system that includes four Scott-Russell linkages for each wheel of a vehicle. The present invention also provides methods for adjusting the ride height of a vehicle.
In one aspect of the invention, a vehicle suspension system for adjusting the ride height of a vehicle is provided. For each wheel of the vehicle, the vehicle suspension system includes four structure arms, with each of the structure arms having an outer control link pivotably attached thereto. The vehicle suspension system also includes four primary links and four inner control arms. One end of each of the primary links is configured to be coupled to a spindle yolk. One end of each of the inner control arms is configured to be coupled to a shock absorber. A torsion spring is provided, and one end of a torsion arm is rigidly attached to the torsion spring. One end of an attachment link is pivotably attached to the other end of the torsion arm. A pin extends through apertures in the attachment link, two of the inner control arms, two of the primary links, and two of the outer control links.
Two translation links are pivotably attached at one end to respective ends of two of the four primary links, and at the other end to respective ends of the other two of the four primary links. Two rotation links are pivotably attached at one end to respective ends of two of the four primary links. The other end of each of the rotation links is configured to be pivotably attached to a frame of the vehicle. A worm gear for rotating the torsion spring is provided. When the torsion spring is rotated, the torsion arm rotates and in turn causes the attachment link to move the pin in an upward or downward direction. The upward or downward movement of the pin causes the four primary links to move in an upward or downward direction to adjust a ride height of a vehicle.
In one embodiment, the vehicle suspension system further includes a second pin that extends through apertures in one of the inner control arms, one of the primary links, and one of the outer control links, and a third pin that extends through apertures in another of the inner control arms, another of the primary links, and another of the outer control links. In one embodiment, the worm gear is manually controlled by a driver of a vehicle from within a cabin of the vehicle. In another embodiment, the worm gear is automatically controlled by a microprocessor. In this embodiment, the microprocessor receives inputs from devices that measure dynamic parameters of the vehicle, e.g., the speed of the vehicle, the pitch and body roll of the vehicle, and the lateral acceleration of the vehicle.
In another aspect of the invention, an adjustable suspension system for a vehicle is provided. The adjustable suspension system includes a torsion spring. For each wheel of the vehicle, linkage means for adjusting a ride height of the vehicle while maintaining a substantially constant camber angle for a wheel of the vehicle is provided. The linkage means is responsive to the torsion spring and is configured to be coupled to a spindle yolk. A means for rotating the torsion spring also is provided. The means for rotating the torsion spring may be either manually controlled by a driver of the vehicle from within the cabin of the vehicle or automatically controlled by a microprocessor.
In yet another aspect of the invention, one method for adjusting the ride height of a vehicle is provided. In this method, four Scott-Russell linkages are provided for each wheel of the vehicle. A torsion spring is rotated to change the orientation of the Scott-Russell linkages to adjust the ride height of the vehicle. In one embodiment, the method further includes maintaining a substantially constant steering ratio as the ride height of the vehicle is adjusted.
In a further aspect of the invention, another method for adjusting the ride height of a vehicle is provided. In this method, four Scott-Russell linkages are provided for each wheel of a vehicle. A dynamic parameter of the vehicle, e.g., the speed of the vehicle, the pitch and body roll of the vehicle, and the lateral acceleration, is sensed. Based on the sensed dynamic parameter, a torsion spring is automatically rotated to change the orientation of the Scott-Russell linkages and thereby adjust the ride height of the vehicle. In one embodiment, the operation of automatically rotating the torsion spring is controlled by the microprocessor. In one embodiment, the method further includes maintaining a substantially constant steering ratio as the ride height of a vehicle is adjusted.
In a still further aspect of the invention, a vehicle having an adjustable suspension system is provided. The vehicle includes a torsion spring, an adjustable suspension system for adjusting the ride height of the vehicle, a worm gear for rotating the torsion spring, and a steering assembly having a flexible cable that allows a substantially constant steering ratio to be maintained when the ride height of the vehicle is adjusted. The adjustable suspension system includes four Scott-Russell linkages for each wheel of the vehicle, with at least one of the Scott-Russell linkages for each wheel of the vehicle being responsive to the torsion spring to adjust a ride height of a vehicle while maintaining a substantially constant camber angle for the wheel.
The present invention provides a number of significant advantages. Most notably, the adjustable suspension system of the present invention enables the adjustment of the ride height of a vehicle over a long range of wheel travel, e.g., at least about 6 inches to about 8 inches, with little or no change in camber angle for each wheel. Because a substantially constant camber angle for each wheel of the vehicle is maintained, wider tires that provide better handling and traction may be used on the vehicle. The four Scott-Russell linkages provided for each wheel resist fore and aft lateral forces on the suspension system. In addition, the steering assembly maintains the steering performance of the suspension system as the ride height is adjusted and thereby eliminates the steering anomaly referred to as xe2x80x9cbump steer.xe2x80x9d